open LOG ">>std.log" or die $!;
im_missing_something_here();
other_calls();
close LOG;

sub im_missing_something_here {
     open STDERR, ">>err.log" or die $!;

     # Perl can run the shell #
     if (open(PIPE, "$cmd <$tempfile |")) {

	     # but there is a message in STDERR #
	     if (-s './err.log') {
		     print LOG "ERROR:see err.log, exiting..\n";
             close STDERR;
		     die "Killed.\n"; #to default STDERR is intent
	}
     ...

}